It would desirable for cost and manufacturability to prepare organic electronic devices such as organic electronic (OE) devices, such as organic field effect transistors (OFETs) or organic light emitting diodes (OLEDs), organic photovoltaics (OPVs) or color filter arrays used in such devices, by deposition of thin film materials (either active or passive materials) in solution on a specific area. Commonly used techniques such as shadow masking using high temperature vacuum deposition are expensive, wasteful of materials and require complicated machinery. One potential solution would be to provide a substrate comprising a patterned bank layer that defines wells into which the active components can be deposited in solution or in liquid form. The wells contain the solution such that the active components remain in the areas of the substrate defined by the wells. The solutions can be introduced into the wells using ink-jet as well as other techniques.
Bank structures, and methods of forming them, are known to be used for defining such confined places (wells) on a substrate. For example, US 2007/0023837 A1, WO 2008/117395 A1, EP 1933393 A1, GB 2,458,454 A, GB 2,462,845 A, US 2003/017360 A1, US 2007/190673 A1, WO 2007/023272 A1 and WO 2009/077738 A1 individually and collectively are representative disclosures of such known structures and methods.
Even if a patterned layer of well-defining bank material is provided, problems still exist in containing the solution within the well region and providing good film formation in the well region using solution processing techniques. Uncontrollable wetting of the well-defining bank layer may occur since the contact angle of the solution on the well-defining bank layer is typically low. In the worst case, the solution may overspill the wells. It is also important that the organic material within the well be as uniformly spread as possible over the entire surface of the bottom of the well. This means that the substrate that forms the bottom of the well and which contacts the organic material should have a low contact angle (high wetting) with organic solutions (see FIG. 1d). However, the contact angle on the substrate cannot be too low for the organic layer as this will lead to the layer having an increased degree of non-uniform thickness, particularly when the well area is very small (see FIG. 1e and FIG. 1f). The combination of bank structures having a high contact angle and a substrate surface having a low contact angle allows for uniform spread of the organic solution within the well, particularly in the edge areas where the substrate and the bank structures meet.
However, the photoresist processes that can be used to create bank structures can affect the wetting properties of the substrate, which is −25 initially covered by the photoresist composition and later removed during processing. A high contact angle for the bank structure is also a very important property for increasing the process window of the printing formulation on the substrate. This is because during the deposition of a solution into the well, the maximum volume that can be deposited and retained in the well could be much larger (2 to 6 times) than the maximum volume of the well if the contact angle of bank with the printed formulation is very high (FIGS. 1a to 1c). This increase in the amount of liquid formulation that can be contained in the well allows for a greater layer thickness that can be achieved. This is particularly important during the preparation of a high resolution device where it is desirable to decrease the pixel size or active area but the thickness requirement for the active layer remains the same or sometimes even higher.
The use of fluorine containing materials in or on such banks in order to modify their wetting properties is well-known. For example, Moon et al, IEEE Electron Device Let., 32(8), 1137 (2011), U.S. Pat. No. 8,765,224, GB 2462845, EP 1905800, WO 03/083960, US 2014/0147950, U.S. Pat. Nos. 7,781,963, 8,217,573, EP 2391187, JP 2008096717, WO 2014/069478 and US 2007/0020899 are individually and collectively representative disclosures of such known structures and methods.
The use of a cresol based novolak (also spelled as novolac) resin is well known as a component for a photoresist. For example, see the section titled “DNQ-Novolac photoresist” in http://en.wikipedia.org/wiki/photoresist. The use of a diazonaphthoquinone (DNQ) photoactive compound (PAC) in such novalak based photoresists is also well known. For example, see http://en.wikipedia.org/wiki/Diazonaphthoquinone. Further information can also be found in Phenolic Resins: Chemistry, Applications, Standardization, Safety and Ecology; A. Gardziella, L. A. Pilato, A. Knop; Springer Science & Business Media, 2000 as well as Diazonaphthoquinone-based Resists; R. Dammel; SPIE Press, 1993. It is also known that one useful class of DNQs are those based on diazonaphthoquinone sulfonate esters of polyhydroxybenzophenones (for example, see U.S. Pat. No. 3,130,048 and JP 9-031044).
U.S. Pat. Nos. 4,587,196, 4,719,167, 4,863,828, 4,906,549, 4,943,511, 5,153,096, 5,478,692 and 5,395,728 describe photoresists using a cresol based novolak resin with 2-diazonaphthoquinone-(4- or 5-) sulfonate esters of various polyhydroxybenzophenones which may optionally contain a surfactant.
US 2012/0287393 describes photoresists using a cresol based novolak resin with 2-diazonaphthoquinone-(4- or 5-) sulfonate esters of various polyhydroxybenzophenones which may optionally contain a fluorosurfactant (among others).
U.S. Pat. No. 6,911,293 describes photoresists using cresol based novolak resins with 2-diazonaphthoquinone-(4- or 5-) sulfonate esters of various polyhydroxybenzophenones with a proprietary fluorosurfactant MEGAFAC R-08 (Dainippon Ink) of undisclosed structure.
JP 08-015858 describes printing plates prepared using photoresists with cresol based novolak resins (among others) with fluorosurfactants such as fluorinated urethanes and 2-diazonaphthoquinone sulfonic acid or polymeric esters thereof. U.S. Pat. No. 4,822,713 and GB 2023858 describe printing plates prepared using photoresists using cresol based novolak resins (among others) with fluorosurfactants such as fluorinated (meth)acrylates and 2-naphthoquinone sulfonic acids or polymeric esters thereof.
U.S. Pat. No. 8,883,402 describes a phototool (a photographic mask or stencil bearing a circuit pattern on a transparent substrate) which includes a fluorinated polyurethane as a release agent. The phototool can be prepared using cresol based novolak resins (among others) with 2-diazonaphthoquinone-(4- or 5-) sulfonate esters of various polyhydroxybenzophenones (among others).
U.S. Pat. Nos. 5,858,547 and 6,517,951 describe the use of cresol based novolak resins with fluorosurfactants (among others) as a planarization layer. Such formulations are thermally set and do not contain a PAC.
U.S. Pat. No. 7,749,676 describes photoresists using cresol based novolak resins with 2-diazonaphthoquinone-(4- or 5-) sulfonate esters of various polyhydroxybenzophenones with a fluorinated silicon resin of high viscosity as a releasing agent.
U.S. Pat. Nos. 7,338,737 and 7,297,452 describe photoresists using alkali-soluble resin (desirably a copolymer that derived from an unsaturated carboxylic acid) with 2-diazonaphthoquinone-(4- or 5-) sulfonate esters of various polyhydroxybenzophenones with a surfactant (desirably, epoxide based fluorosurfactants among others).
U.S. Pat. No. 5,368,975 describes a negative-working photoresist using a novolak resin (among others), a diazonaphthoquinone sulfonic ester (among others) and a non-ionic oligomeric urethane compound. The urethane compound contains a poly(ethylene oxide)3-25 group as well as aromatic rings. Although trifluoromethyl groups are disclosed as a optional substitutent on the aromatic rings, the overall fluorine content of the entire molecule would be very low.
U.S. Pat. No. 4,613,561 describes an aqueous alkaline two-step developing method for a positive photoresist where the developer includes a fluorosurfactant.
U.S. Pat. No. 7,449,280 describes a photoresist composition which can contain a urethane fluorosurfactant (among others).
However, in spite of all of these investigations, there is still a need to provide photoresist compositions that provide well structures with the necessary wetting properties. Thus it would be desirable to provide positive or negative working photoresist compositions for use in forming bank structures that are compatible with ink-jet printing and photolithography which provide desirable solution-containing properties.
Additionally it would be desirable to provide high resolution methods of forming such bank structures using methods that are both compatible with ink-jet printing and photolithography and do not require the use of processes such as halocarbon reactive ion etching or other post-formation treatments. Still further it would be desirable to provide OE devices or color filter arrays manufactured using such desirable structure defining materials and structure forming methods. Finally, there is a need to provide small active areas with uniform film thickness in the wells between the bank structures.